Thermionic valve



Nlay 16, 1933.

H. J. ROUND 1,909,594

THERMIONIC VALVE Fi'led Sept. '7, 1928 INVENTOR H Nm JOSEPH ROUND BY A ORNEY Patented May 16, 1933 UNITED STATES earner omer.

HENRY JOSEPH ROUND, F LONDON, ENGLAND, ASSIGNOR TO RADIO CORPORATION 0F AMERICA, A CORPORATION 0F DELAWARE THERMIONIC VALVE Application led. September "I, 1928, Serial No. 304,480, and in Great Britain September 23, 1927.

This invention relates to thermionic valves, and more particularly to the so-called screened grid thermionic valves in which an electrostatic screen is interposed between an input electrode and an output electrode.

According to this invention a thermienic valve is provided with two or more electrostatic screens interposed between an input and an output electrode of the valve.

The invention is illustrated in the accompanying drawing in which;

Figure l shows a valve constructed in accordance with my invention while:

Figure 2 shows a modification of the valve of Figure l.

Referring iirst to Figure l, which shows one form of construction, a thermionic valve comprises live transversely arranged electrodes, namely, a filament l, a control grid 2 formed as a flattened helix surrounding the filament, an anode 3 and two electrostatic screening grids 4 and 5, arranged one. behind the other between the control grid and the anode. rFhe screening'grids are formed of open mesh, the grid being provided with an annular flange in part enclosing the anode.

In operation the screening grids, which preferably extend substantially to the walls ot the valve, are connected to suitable sources ci static voltage such as batteries through nonsinductive connections whereby they are maintained at definite constant potentials, but will be at Zero potential. In the arrangement shown in Figure l, the filament, control grid and the screening grid 4 are stemmed7 to one footstep 6 of the valve, which is formed double-ended, the screening grid and the anode being stemmed to the other foot-y step 7.

In the modiiication shown in Figure 2, a second control grid 8'is connected in parallel with the control grid 2 normally provided and is located between the two screening grids. ln operation the control grids are maintained with negative potential bias and the screening grids with positive potentia bias. In the arrangement shown in Figure 2, the additional control grid 8 is stemmed at one end of the valve, together with the filament 1, control grid 2 and irst screening grid 4, the screen screening grid 5 and anode 3 being stemmed at the other end of the valve.

ln Figure 2 ther control grids are shown as constituted each by parallel wires stretched velope a cathode, two parallel control grids connected together within said envelope, two separate electrostatic screens, and an anode, one of said screens being located between the control grids, and the other between the anode and the control grid nearest adjacent thereto.

2. A thermionic tube comprising an envelope enclosing a cathode, an anode, two parallel grid electrodes interposed between said cathode and ano-de and connected together inside said envelope, and two separate electrostatic screens parallel to said grid electrodes, one of said screens being interposed between said connected grid electrodes and the other screen adjacent said anode.

3. A thermionic tube comprising an envelope enclosing a cathode, an anode, two parallel grid electrodes interposed between said cathode and anode and connected together inside said envelope, and two separate electrostatic screens parallel to said grid electrodes, one of said screens being interposed between one of said grid electrodes and said anode, and the other screen being adjacent the other of said grid electrodes.

4. A thermionic tube comprising an envelope enclosing a cathode, an anode, two parallel grid electrodes interposed between said cathode and anode and connected together inside said envelope, and two separate electrostatic screens parallel to said grid electrodes, one of said screens being interposed between said connected grid electrodes and the other of said screens being mounted outside said connected grid electrodes.

5. A thermionic tube comprising an envelope enclosing :L cathode, an anode, tWo parallel grid electrodes interposed between said cathode and anode and connected together inside said envelope, and two separate electrostatic screens associated With said grid electrodes and mounted parallel to said grid electrodes between said cathode and said anode.

HENRY JGSEPH ROUND. 

